Meeting Abstract
Trees allocate carbon (C) from sources to sinks by way of a series of processes involving carbohydrate transport and utilization. Yet it is unclear how these dynamics will respond to a warmer world. We conducted a warming and pulse‐chase experiment on Eucalyptus parramattensis growing in a whole‐tree chamber system to test whether warming impacts C allocation by increasing the speed of carbohydrate dynamics. We pulse‐labelled large, field-grown trees with 13C‐CO2 to follow recently fixed C through aboveground and belowground organs by using compound‐specific isotope analysis of sugars. We then compared concentrations and mean residence times of individual sugars between ambient and warmed (+3°C) treatments. Trees dynamically allocated 13C‐labelled sugars throughout the aboveground‐belowground continuum. However, we did not find a significant treatment effect on C dynamics, as sugar concentrations and mean residence times were not altered by warming. From the canopy to the root system, 13C enrichment of sugars decreased, and mean residence times increased, reflecting dilution and mixing of recent photoassimilates with older reserves. Interestingly, the presence of raffinose in the phloem provides evidence for a polymer trap mechanism for phloem loading. Our results suggest that a locally endemic eucalypt was able to adjust its physiology to warming representative of future temperature predictions for Australia.
